1. Field of the Invention
The present invention relates to a production method of a substrate for a liquid crystal display in which a color filter or a black matrix is directly formed on a TFT substrate on which a thin film transistor is formed for each pixel region, and in particular, relates to a production method of a substrate for a liquid crystal display in which a predetermined exposure pattern is formed in a predetermined position of the TFT substrate at a high level of precision, by detecting a reference position preset in a pixel region that has been image-captured while the TFT substrate was carried at a predetermined velocity, and controlling irradiation timing of exposure light.
2. Description of the Related Art
In general, a liquid crystal display has a configuration such that a liquid crystal is sealedly arranged between a pair of transparent substrates arranged opposing each other. In this case, one of the transparent substrates becomes a TFT substrate in which in an arrayed pixel region there are formed a pixel electrode and a thin film transistor, and a wiring for driving the thin film transistor is arranged around the pixel region. Moreover, the other of the transparent substrates becomes a color filter substrate in which a black matrix is formed so as to correspond to the thin film transistor and the wiring, a color filter is formed so as to cover pixels of the black matrix, and a common electrode is formed on the black matrix and the color filter. In the liquid crystal display of such a configuration, the line width of the black matrix is generally designed wide in consideration of alignment error in the above pair of transparent substrates. Therefore, in the conventional liquid crystal display, miniaturization of pixel regions has been difficult because it causes a reduction in the aperture ratio of the pixel of the black matrix.
On the other hand, a production method of a substrate for a liquid crystal display being a so called “color filter on TFT” that addresses the above problem, in which a color filter is formed so as to cover the thin film transistor and the wiring arranged around the pixel region of the TFT substrate, has been proposed (for example, refer to Japanese Unexamined Patent Publication No. 2004-70196).
However, in such a conventional production method of a substrate for a liquid crystal display, the exposure step for forming exposure patterns of the color filter and the black matrix on the pattern for the thin film transistor and the wiring of the TFT substrate is performed by mutually matching an alignment mark formed around the TFT substrate with an alignment mark of the mask of the color filter or the black matrix. Therefore, a high level of dimension precision has been required for positioning of each of the alignment marks and arrangement of each of the patterns. In particular in the case of a substrate for a large display, this requirement is even stricter, to have resulted in making positioning of each pattern more difficult. Accordingly, overlapping precision for the color filter and the black matrix formed on the pattern for the thin film transistor and the wiring cannot have been sufficiently improved. As a result, the line width of the black matrix cannot have been made narrow and thus, miniaturization of each of the pixel regions while suppressing a reduction in aperture ratio cannot have been successfully achieved. Therefore, a high definition liquid crystal display could not be realized.